Automotive airbag installations normally employ an inflator to produce the gases required to inflate an airbag. Such inflators commonly employ a pyrotechnic material which either acts alone to produce the gas or serves to release stored supplemental gas. Inflators of the latter type are known as "hybrid" inflators. One example of a hybrid inflator will be found in co-pending U.S. patent application Ser. No. 08/321,786 filed Oct. 12, 1994 by R. J. Clark et al. for "Stamped Metal Toroidal Hybrid Gas Generator with Sliding Piston" and assigned to the same assignee as the present invention. The disclosure of that application is incorporated by reference herein.
After the occurrence of an accident and subsequent airbag deployment, it would be desirable to ascertain whether or not the inflator performed adequately. By "adequately" is meant whether the inflator functioned to provide gas at a sufficiently high pressure, i.e. at least at a predetermined minimum operating pressure, to inflate the airbag within the necessary time period. If, for example, a hybrid type inflator had a slow leak permitting the escape of the pressurized inert gas stored therein, the pressure produced by the pyrotechnic material alone or in combination with the remaining stored gas might be inadequate to reach the predetermined minimum operating pressure. However, this would not be readily ascertainable merely from a post-inflation inspection of the inflator.
Accordingly, it is a primary object of the present invention to provide a method and apparatus for readily determining, by a post-inflation inspection, if the inflator functioned properly by producing inflation gases at or above a predetermined minimum operating pressure. It is also an object of the invention to provide such a post-inflation inspection that does not require dissecting or disassembling the fired inflator and requires no electronics or electrical circuitry. A still further object of the invention is to provide for such post-inflation inspection without requiring any additional components. Other objects, features, and advantages will become apparent from the following description and appended claims.